1. Field of the Invention
The present invention relates to an antistatic socket apparatus that can be brought into contact with leads of a semiconductor device for allowing electrical conduction to take place between a measurement instrument and the semiconductor device.
2. Description of Related Art
When measuring electrical characteristics of a semiconductor device, the internal elements of which are sealed in a package made up of a non-conductive material such as resin, a special-purpose socket is used for allowing electrical conduction to take place between leads of the semiconductor device and a measurement instrument.
The socket mainly comprises a bearer, which is made up of a non-conductive material and has a mounting surface for mounting a semiconductor device, and metallic contactors arranged on the circumference of the bearer to be brought into contact with leads of the semiconductor device mounted on the mounting surface of the bearer.
When measuring electrical characteristics of a semiconductor device by way of this socket, the socket is connected to a measurement instrument in advance, and with the socket connected to the measurement instrument, the package of the semiconductor device is mounted on the mounting surface of the socket's bearer.
Then by slightly pressing the package, the leads of the semiconductor device can be brought into contact with the contactors of the socket, allowing electrical connection to be established between the semiconductor device and the measurement instrument.
In this state, predetermined signals are transmitted from the measurement instrument to the semiconductor device. Receiving these predetermined signals, the semiconductor device outputs response signals for use in the measurement of the semiconductor device's characteristics.
However, such a socket for measuring electrical characteristics of a semiconductor device has the following problem.
When the package of a semiconductor device is mounted on the mounting surface of the socket, contact friction is developed between the bearer of the socket and the package. Static electricity generated by the friction is accumulated inevitably inside the bearer which is made up of a non-conductive material.
For example, when using a bearer made up of polyethelimide (referred to hereafter as PEI) with a resistance value in the range 10.sup.16 to 10.sup.17 ohms, mounting and dismounting a semiconductor device more than 1,000 times onto and from the mounting surface of the bearer will accumulate static electricity in the bearer, giving rise to a voltage of more than 500 V.
In particular, the bearer of the socket uses a floating mechanism which insulates it and which forms a structure which prevents ready discharge of the accumulated static electricity.
With static electricity of such a high voltage accumulated in the bearer, bringing leads of a semiconductor device into contact with the contactors of the socket will cause the accumulated static electricity to be discharged through the semiconductor device, bringing about damage to the internal elements of the semiconductor device.
In order to prevent the internal elements from being damaged by such static electricity, ions bearing electric charge of a polarity opposite to the charge of the static electricity are blown against the socket to suppress the amount of the static electricity to a voltage of typically lower than 100 V. However, the complexity of the ion blowing process gives rise to other problems.